1. Field of the Invention
The present invention relates to a combination lock that may prevent inadvertent change in the unlocking code. The present invention also relates to a combination lock that has a better rotational positioning effect for each number wheel and that provides a sound for indicating rotation of each number wheel.
2. Description of the Related Art
Combination locks provide a convenient tool for users, as keys are not necessary. Traditional combination locks have fixed unlocking code when manufactured and are thus easily unlocked by unauthorized individuals. FIG. 6 of the drawings illustrates a conventional lock allowing change in the unlocking code. The lock has a male lock body 1' and a female lock body 2'. The female lock body 2' includes a recessed chamber 21' in a first side thereof and a groove 22' in a second side thereof. A stem 23' extends from the first side of the female lock body 2' for mounting an elastic element 24', a number of slide sleeves 25', a number of positioning resilient plates 26', a number of retainer plates 27', a number of number wheels 28', a control slide sleeves 29', and an end cap 20'. Each retainer plate 27' has a slit 271' and a number of teeth 272' on a side thereof. Each number wheel 28' has a number of annularly disposed engaging grooves 281'.
FIG. 7 illustrates a sectional view of the combination lock in FIG. 6. When change in the unlocking code is required, the control sleeve 29' is actuated to move the retainer plates 27' and slide sleeves 25. The teeth 272' on each retainer plate 27' disengage from the engaging grooves 281' of the associated number wheel 28', thereby allowing adjustment in the unlocking code by rotating the number wheels 28'.
Nevertheless, the above-mentioned adjustment can be proceeded even though the combination lock is in a locked status (i.e., the slits 271' of the retainer plates 27' are not aligned with each other). As a result, the user may not know the correct new unlocking code. In addition, the adjustment is inconvenient to the user, as the user has to exert a continuous force to the control sleeve 29' until the new unlocking code is set. In addition, the teeth 272' of each retainer plate 27' may be not completely disengaged from the engaging holes 281' of the associated number wheel 28' and thus result in malfunction of the combination lock, as the correct unlocking code cannot be known. Assembly of the combination lock is time-consuming and inconvenient, as a slide sleeve 25', a positioning resilient plate 26', and a retainer plate 27' are required for each number wheel 28'.
FIGS. 8 and 9 of the drawings illustrate a positioning plate 3' for a combination lock. The positioning plate 3' includes a recessed section 31' and a channel 32' for holding an elastic element 33' having an end 331' that will produce a sound when impinged by an inner periphery of an associated number wheel 4'. It is, nevertheless, found that the elastic element 33' is apt to be disengaged from the positioning plate 3'.
The present invention is intended to provide a combination lock that mitigates and/or obviates the above problems.